1. Field of the Invention
The present invention relates to a combination stopper and shield closure for body fluid collection tubes and, more particularly, relates to an improved combination stopper and shield closure for an evacuated body fluid collection tube having a minimal cross-section at the point of needle penetration together with increased retention against needle sleeve push-back when the needle is being pushed through the stopper.
2. Background Description
An evacuated blood collection tube is commonly used by a doctor, phlebotomist or nurse to draw a sample of body fluid from a patient in a hospital or doctor's office for diagnostic testing. During the use of such a tube a double-ended needle in a needle holder is inserted in a vein of the patient, and the closed evacuated tube is inserted into the open end of the holder until the needle in the holder pierces the tube's closure. The blood collection tube contains a vacuum that then draws a body fluid sample from the patient into the tube. Therefore, it is important for the closure on the tube to fit securely on the open end of the tube and maintain the vacuum in the tube before, during and after the blood collection procedure.
Current closures for evacuated blood collection tubes include plastic shields containing a rubber stopper, wherein the stopper is thick or has an enlarged head to fit snugly within and remain attached to the shield and a plug portion that fits in the open end of the tube. Retention of the stopper in the shield is important when the shield and stopper are being removed from the open end of the tube so that blood within the tube can be tested. An example of a closure of the type discussed above is found in U.S. Pat. No. 4,967,919 (Earhart), which relates to a blood collection assembly having an enlarged rubber stopper within a cap that are both mounted on an open end of a blood collection tube to seal the tube.
It is also important, of course, for the vacuum in the tube to be sufficient to draw body fluid into the tube, since body fluid must be drawn as quickly as possible to minimize the amount of time a patient has one end of the needle in their body, which can be uncomfortable and cause pain. For example, if the vacuum in the tube is deficient, subsequent removal of the tube from the needle holder and insertion of another tube in the needle holder would be necessary which prolongs the unpleasant procedure. Therefore, it is important that the closure fit within the open end of the tube to retain the vacuum in the tube before, during and sometimes after use.
Currently the design of closures has required a trade-off between the force necessary for inserting a needle through the rubber stopper and into the tube to draw body fluid into the tube and the force needed to withdraw the closure from the tube in the laboratory. Using plastic shields over rubber stoppers has provided a sufficient gripping surface to enable a user to easily remove the stopper from the evacuated tube and overcome the force of the vacuum within the tube. However, rubber stoppers have commonly been so thick that increased force is necessary for the needle to penetrate through the stopper into the tube.